1. Field of the Invention
The present invention relates to a force sensitive switch. More particularly, the switch, when force is applied against a section thereof, is operative to stop a machine or the like until a structure of the machine producing the force on the switch, is repositioned.
2. Prior Art
The existing art for such devices uses roller switches or rubbing blocks for force detection. The roller switch, when contacted by a misaligned belt, for example, has a spring loaded arm which rotates about a pivot, when the arm has rotated beyond a predetermined point, the switch gives a signal by closure of contacts or the like. The roller mounted upon the pivoted arm is free to rotate about its own axis so that contact with the moving belt will not cause undue wear.
When a belt is partially misaligned, sufficient to contact the roller but insufficient to cause machine stoppage, the roller rotates continuously, generating heat, and becoming a maintenance hazard.
An alternative type of detector, known generally as a rub block or rubbing block, is made from substantially rigid material containing, embedded therewithin, a temperature detector. When used in the above described application, when the moving belt contacts the rubbing block applying force thereagainst, the rubbing block becomes heated and when the preset temperature is reached, the temperature sensor generates a signal to stop the machine. This type of detector is hazardous as heat must be generated for the device to operate.
According to the invention there is provided a force sensing switch comprising a housing and a movable member movable relative to the housing upon having a predetermined force applied thereagainst by an adjacent moving structure when the structure becomes misaligned, the movable member engaging circuitry within the housing which will produce an alarm and will stop the adjacent structure from moving.